Method of producing coatings on hard metal bodies

ABSTRACT

A (solid solution) layer (of) comprising one or more of the carbides of the metals titanium, vanadium, tantalum, or columbium (, or their carbides,) is formed on the surface of a hard metal body, such as tungsten carbide, by heating the hard metal body in contact with the coating metal, or an alloy, or a readily decomposable compound thereof, at a temperature above about 900*C., or by electrrolytic deposition, followed by heating.

United States Patent 1 1 E Re. 28,485

Rix et al. 3 Reissued Jul 15, 1975 [54] METHOD ()1 PRODUCING OATINGS 0N 1465,32; 3/1949 Murray .1 204/37 R 1 2.570.248 lU/l95l Kelley H 29/473l HARD METAL BODIES 3.685.543 8/l954 Sindebund 148/6 [75] inventors: Walter Rix; Grete Dix, both of 10011593 M961 Krcuchcn et al. .1 H1 21? Essen. Germany 3.| 7|.l92 3/1965 Ortner et al. 75/203 3172.963 9/1966 Wussermun et ul 117/205 X [731 Assgneel Frled- KruPP Geseuscha 3.334.975 8/1967 Quuss et ul. 29/5114 beschrankter flaming Essen 3.393.084 7/1968 Hurlwig .1 117 1 18 x any 3.398.256 8/1968 Foley 2 1/5114 l l Filed; Jan. 24. 1973 FOREIGN PATENTS OR APPLICATIONS [2 [1 Appl. No: 326,276 7l(7.(l34 9/1954 United Kingdom 75/203 722.916 2/1955 United Kingdom/1., .1 Ill/'1 l8 Related Pale"! Documents 766.059 1/1957 United Kingdom 11111111111111111 75/203 Reissue of:

[64] Patent No.: 3,558,445 Primary E.\111niner-F. Fmundson Issued: Jan. 26, 1971 AHUIHI)" Agent, or FirmSpencer & Kaye Appl No: 641,474 Filed: May 26, 1967 57 ABSTRACT [52] U 5 Cl 29/198, H7 204/37 A I: Solid Solution 1 layer 0f wmpriising one or 204/38 more ufrlie carbides of the metals titanium. vanadium. I5 I 1 1m CI C2 7/00, C2 17/00 C23!) 5/52 tantalum, or columbium [or their carbides] is formed [58] Mei! 'i'sg 204/37 38 R 38 on the surface ofa hard metal body, such as tungsten i carbide, by heating the hard metal body in contact with the coating metal, or an alloy, or a readily de- [56] Re'eremes cued composable compound thereof. at a temperature above about 900C. or by electrolytic deposition. UNITED STATES PATENTS followed by heating 898.979 9/l9U8 Kuzel 29/504 2.456.761 12/1 /411 Williams .1 29/5114 10 Claims. No Drawings METHOD OF PRODUCING COATINGS ON HARD METAL BODlES Matter enclosed in heavy brackets I: 1 appears in the original patent but forms no part of this reissue specification: matter printed in italics indicates the additions made by reissue.

BACKGROUND OF THE INVENTION it is well known that titanium carbide at elevated temperatures readily and rapidly incorporates large amounts of tungsten or tungsten carbide into its lattice. whereas tungsten carbide does not correspondingly absorb titanium or titanium carbide. or only in very small amounts. Therefore. in a mixture of titanium carbide and tungsten. the tungsten is taken up by the titanium carbide to a considerable percentage as the temperature increases.

It is further known that in a mixture of titanium. tungsten and carbon. I solid solution is I mixed crystals are formed with the titanium carbide lattice at elevated temperature. Only when the amount of tungsten exceeds the solubility limits for tungsten in titanium carbide. is tungsten carbide formed. These circumstances apply correspondingly to the metals vanadium. tantalum. and columbium. as well as to their carbides.

SUMMARY OF THE lNVENTlON in accordance with the present invention. there is provided a process for the preparation. upon the surface ofa hard metal (cemented carbide) body containing tungsten carbide of a I: solid solution layer I of 1 comprising titanium carbide. vanadium carbide. tantalum carbide and/or columbium carbide I; with tungsten carbide I This layer exhibits good adhesion to and coalescence with the hard metal body surface.

The present invention comprises forming said solid solution layer by the reaction of any of the metals titanium. vanadium. tantalum. or columbium. or their alloys or readily decomposable compounds. individually or in combination. with the tungsten carbide of a hard metal body. on the surface of the hard metal body. at elevated temperature. The invention is based upon the principle that in a mixture of tungsten carbide with one or more of the aforementioned metals, or their alloys. or readily decomposable compounds. such as. for example. titanium hydride. or titanium tetrachloride. the tungsten carbide does not take up any titanium. but rather, the tungsten carbide is decomposed, and titanium carbide is formed I: and the latter absorbs the liberated tungsten into its lattice DESCRIPTION OF THE PREFERRED EMBODIMENTS in accordance with one embodiment of the invention. the new method can be advantageously carried out in such manner that the hard metal body is embedded in titanium hydride powder. heated under cover of a protective gas to a temperature above about 900C. and held at this temperature for the desired period of time.

In accordance with another embodiment of the invention. the hard metal body is heated in vacuum with titanium vapor and finally maintained for the desired time at a temperature above about 900C.

in accordance with another embodiment. the hard metal body is exposed to the vapor ofa volatile. readily decomposable titanium compound at elevated temperature; advantageously there can be employed for this purpose titanium tetrachloride vapor at a temperature above about 900C. The higher the temperature of the treatment. the more rapid is the formation of the desired I: solid solution 1 layer.

in accordance with still another embodiment of the invention. the hard metal body is coated with a layer of titanium electrolytically. and then maintained in a vacuum or under a layer of protective gasi'or the desired period of time at a temperature above about 900C in place of titanium or its compounds or alloys. there can also be employed. correspondingly. the decomposable compounds or alloys of the metals vanadium. tantalum. and columbium.

Examples of suitable alloys of titanium and of the other metals include: 30% Ti. V: 10% Ti. 90% Cb; Ti. 20% Ta; 50% V. 50% Cb; 20% V. 80% Ta; 40% Cb. 60% Ta: 30% Ti. 30% V. 40% Cb: 10% Ti. 30% Cb. 60% Ta: 70% V. l5% Cb. 15% Ta. 25% Ti. 25% V. 25% Cb. 25% Ta.

Examples of suitable decomposable compounds of titanium. and of the other metals include: TiClr. TiBn: Tilt; V1 VCL; CoClfi; TaCl TaBr...

The upper limit of temperature of heating employed may vary within a wide range. but will generally not exceed about i800C.

Examples of protective or inert gases which may be employed in performing the process of the invention include: Hydrogen. helium. argon. neon. krypton. and mixtures thereof.

Typical compositions of the hard metal body include: 98% WC. 2% Co; 70% WC. 30% Co; 60% TiC. 35% WC. 5% C0; 5% TiC. WC. 10% Co: 5% TaC. 85% WC. 10% Co.

The proportions of the coating metals or their compounds or alloys to those of the hard metal body may vary widely. but in general will range from about 0.0l to about 2 parts per 100 parts of hard metal body. by weight.

Where a powder is used for embedding purposes the average particle size is about 10am.

Where a vacuum is used. the range will be about l0--'* mm. Hg. to the highest vacuum obtainable.

EXAMPLE I in a vacuum of l0- mm. Hg. titanium metal is heated to a temperature of i260C.. and by this means a titanium layer is vaporized upon a hard metal body consisting of WC and 10% Co held at a temperature of 30C. The hard metal body coated with this titanium layer is then heated. under argon. to a temperature of l000C. and held at this temperature for a period of i5 minutes.

EXAMPLE ii A hard metal body consisting of 5% TaC. 85% WC and 10% Co is embedded in fine-grained titanium hydride powder having an average particle size of i0 pm. is heated. under hydrogen. to a temperature of l000C. and held at this temperature for a period of [5 minutes.

EXAMPLE iii A hard metal body consisting of 70% WC and 30% Co is embedded in a fine-grained powder of a 20% vanadium. 80% tantalum alloy having an average particle size of 10 um. and held. under helium. at a temperature of l200C. for a period of half an hour.

EXAMPLE [V A hard metal body consisting of 20% TiC, 70% WC and l% Co is exposed for a period of half an hour to a hydrogen flow carrying vaporized titanium tetrachlo ride. at a temperature of 1050C. The grain size ofthe coating is 1 am to pm.

EXAMPLE V in a process as described by M. E. Sibert and M. A. Steinberg in Journal of Electrochemical Society. vol. 102 (I955), p. 64l to 647 a hard metal body consisting of 98% WC and 2% Co is electrolytically coated with a titanium layer having a thickness of about 5 am, and is then held. under hydrogen. at a temperature of 1 100C. for a period of half an hour.

It will be understood that the above description of the present invention is susceptible to various modifications. changes and adaptations. and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. A process for forming a solid solution .1 layer on a surface of a hard metal body containing tungsten carbide. the layer comprising at least one member selected from the group consisting of titanium carbide. vanadium carbide. tantalum carbide and columbium carbide. comprising applying to the surface ofthe hard metal body a coating of (a) at least one member se kected from the group consisting of titanium. anadium, tantalum. and columbium. (bl alloylsl of la] or (cl readily decomposable compoundls] ofta) and subjecting said surface of the hard metal body to an elevated temperature above about 900C. for a period sufficient for forming the I: solid solution layer thereon.

2. The process of claim 1 in which the surface is subjected to the elevated temperature under vacuum.

3. The process of claim 1 in which the surface is sub jected to the elevated temperature under a protective gas cover.

4. The process of claim 1 in which the coating is applied to the hard metal body surface by vapor coating.

5. The process of claim I in which the coating is applied in vapor form at elevated temperature.

6. The process of claim I in which the coating is applied electrolytically. followed by heating at elevated temperature.

7. The process of claim 6 in which said heating takes place in a vacuum.

8. The process of claim 6 in which said heating takes place under a protective gas.

9. A process according to claim 1 wherein the solid solution layer comprises titanium carbide.

10. A hard metal body containing tungsten carbide and having a surface coated with a I: solid solution layer comprising at least one member selected from the group consisting of titanium carbide. vanadium carbide. tantalum carbide and columbium carbide,

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UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT Nb. 1 Re 28,485

DATED July 15th, 1975 |NV ENTOR(S) I Walter Rix et a].

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the patent, insert [30] Foreign Application Priority Data June 2, 1966 Germany l52ll66-.

Signed and ,fiealcd this A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissimier ufPatems and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. Re 28,485

DATED July 15th, 1975 INVENTOR(S) Walter Rix et a1 It IS certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 26, change @001 to -CbCl Signed and Sealed this Arrest.-

RU'I'II C. MASON Alluring Officer C. MARSHALL DANN (nmmiuiuner vfParem: and Trademarks 

1. A process for forming a (solid solution) layer on a surface of a hard metal body containing tungsten carbide, the layer comprising at least one member selected from the group consisting of titanium carbide, vanadium carbide, tantalum carbide and columbium carbide, comprising applying to the surface of the hard metal body a coating of (a) at least one member selected from the group consisting of titanium, vanadium, tantalum, and columbium, (b) alloy(s) of (a) or (c) readily decomposable compound(s) of (a) and subjecting said surface of the hard metal body to an elevated temperature above about 900*C. for a period sufficient for forming the (solid solution) layer thereon.
 2. The process of claim 1 in which the surface is subjected to the elevated temperature under vacuum.
 3. The process of claim 1 in which the surface is subjected to the elevated temperature under a protective gas cover.
 4. The process of claim 1 in which the coating is applied to the hard metal body surface by vapor coating.
 5. The process of claim 1 in which the coating is applied in vapor form at elevated temperature.
 6. The process of claim 1 in which the coating is applied electrolytically, followed by heating at elevated temperature.
 7. The process of claim 6 in which said heating takes place in a vacuum.
 8. The process of claim 6 in which said heating takes place under a protective gas.
 9. A process according to claim 1 wherein the (solid solution) layer comprises titanium carbide.
 10. A HARD METAL BODY CONTAINING TUNGSTEN CARBIDE AND HAVING A SURFACE COATED WITH A (SOLID SOLUTION) LAYER COMPRISING AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF TITANIUM CARBIDE, VANADIUM CARBIDE, TANTALUM CARBIDE AND COLUMBIUM CARBIDE. 